Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires http-interop/http-factory-tests ^0.9.0 -> satisfiable by http-interop/http-factory-tests[0.9.0]. - http-interop/http-factory-tests 0.9.0 requires phpunit/phpunit ^6.5 || ^7.0 || ^8.0 || ^9.0 -> found phpunit/phpunit[6.5.0, ..., 6.5.14, 7.0.0, ..., 7.5.20, 8.0.0, ..., 8.5.34, 9.0.0, ..., 9.6.13] but it conflicts with your root composer.json require (^10.0.0). Problem 2 - Root composer.json requires php-http/psr7-integration-tests ^1.3 -> satisfiable by php-http/psr7-integration-tests[1.3.0]. - php-http/psr7-integration-tests 1.3.0 requires phpunit/phpunit ^8.0 || ^9.3 -> found phpunit/phpunit[8.0.0, ..., 8.5.34, 9.3.0, ..., 9.6.13] but it conflicts with your root composer.json require (^10.0.0). Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.